Characterizing Physicochemical Evolution of Biomass Particles during Fast Pyrolysis Using High-Resolution Simulation

点击翻译按钮获取中文摘要

Fast pyrolysis is a prominent technology in converting waste biomass to combustible gases and liquids; pyrolysis also occurs at the early stage of solid fuel combustion. Fast pyrolysis-derived liquid fuels are regarded as an economically feasible alternative to fossil fuels and some facilities for heat and power generation have been brought online in recent years. However, despite its promising potential, the development of fast pyrolysis has been hindered by the complexity of reactor conditions in biomass pyrolysis, and to date, methods capable of predicting the detailed processes are unavailable. The objectives of this project are to characterize accurately the behaviors of biomass particles and predict the product yields of a fast pyrolysis reactor by using high-fidelity numerical simulations. The proposed research activities will lead to advances in the fundamental science of biomass pyrolysis for energy applications. The educational activities are to engage K-12 science teachers in research in order to promote education on renewable energy. In the U.S., a significant number of K-12 science teachers have not majored in the physical sciences. The research training of K-12 science teachers can enrich their critical thinking and enable them to incorporate their new knowledge into their classroom teaching.The proposed research plan is to conduct high-resolution simulations of biomass fast pyrolysis and to derive submodels for use in engineering CFD codes. A novel simulation approach, one that combines the lattice Boltzmann method, discrete element method, chemical kinetics, and particle shrinkage modeling, will be employed to describe the physicochemical evolution of biomass particles. Computational results will be validated by experimental data. Based on the simulation results, a drag coefficient model will be derived and tested. This work will address several scientific topics of paramount importance to biomass pyrolysis: physicochemical changes of particles, particle-particle and gas-particle interactions, and effects of particle properties and operating conditions on the pyrolysis products. The underlying difficulty of designing and optimizing an efficient biomass reactor is the lack of fundamental understanding of particle behaviors under realistic conditions. This research will characterize intra-particle transport, flow fields smaller than particle size, chemical reactions, and evolutions of particle size and properties. The resulting open-source code can be used by the scientific community as a baseline tool for further advanced numerical study on the pyrolysis of solid particles, e.g., coal, wood chips, municipal solid waste, or polymer materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.